The present invention relates to catheter based pressure sensing systems for diagnosing female urinary incontinence, and in particular to systems for determining the relationship between urethral pressure and vesicle pressure in response to changes in abdominal pressure. Preferred aspects of the present invention relate to urethral catheter holder mechanisms.
Female urinary incontinence can be evaluated by determining the relationship between a patient""s urethral pressure and her vesicle (ie: bladder) pressure. Specifically, incontinence will occur when her vesicle pressure exceeds her urethral pressure. A continence margin can thus be defined by the difference between the patient""s urethral pressure and the vesicle pressure.
Both urethral pressure and vesicle pressure will change in response to changes in abdominal pressure, however, the urethral and vesicle pressures may change at different rates as the abdominal pressure changes. Accordingly, incontinence may occur at various abdominal pressures at which the vesicle pressure exceeds the urethral pressure. Incontinence can therefore be evaluated by producing a pressuregram showing the relationship between the urethral pressure and the vesicle pressure of the patient at different abdominal pressures.
Measuring the patient""s vesicular and urethral pressures with a pressure sensing catheter can be accomplished by moving a pressure sensor on the catheter from the patient""s bladder, (at which the vesicle pressure is measured), through the patient""s urethra (at which maximum urethral pressure is measured). Specifically, a urinary catheter with internal or external pressure transducers can be used to take pressure measurements at the proximal urethra, mid-urethra, and distal urethra. Typically, such a pressure sensing catheter is first introduced through the urethra into the bladder. The pressure sensing catheter is then withdrawn through the urethra with pressure measurements taken at the proximal urethra (being 5-10 mm from the urethro-vesicular junction), the mid-urethra (being the point of maximum resting urethral pressure) and the distal urethra, (being 5-10 mm from the external meatus).
The measurements of the patient""s vesicular and urethral pressures are preferably taken at various abdominal pressures. Such different abdominal pressures can conveniently be generated simply by having the patient cough with different amounts of effort. For example, a mild couch would generate a minimal increase in abdominal pressure, whereas a more intense cough will generate a greater abdominal pressure. The increase in abdominal pressure will cause both the urethral and vesicle pressures to increase.
Unfortunately, such coughing will also tend to cause movement of the patient""s bladder and urethra. As such, it is difficult to maintain the position of the pressure sensing catheter relative to the urethra during the jarring movement of the urethra caused by the patient coughing. Unwanted movement of the catheter relative to the urethra caused by the jarring action of the patient coughing tends to compromise the accuracy of the pressure measurements.
It is important, therefore, to maintain the catheter at each of the desired measurement positions in the urethra when taking the pressure measurements. To date, an effective solution for maintaining the position of the pressure sensing catheter at preferred locations along the urethra when the urethra moves in response to the patient""s cough have not been found.
The present invention provides a female urethral catheter holder which is adapted to support a pressure sensing catheter such that the catheter can be positioned at various desired locations along the patient""s urethra, allowing for the catheter to move in response to urethral movement, such that a pressure sensing transducer disposed on the catheter does not move relative to the urethra when the patient coughs.
In a preferred aspect of the present invention, the urethral catheter holder comprises a supporting base, which is adapted to register against the labia of the patient; a suspension housing mounted to the supporting base; a catheter securement device, (which is adapted to move within the suspension housing when the patient coughs such that the catheter moves with the urethra); and a biasing device. In preferred aspects, the catheter securement device comprises a catheter guide which is adapted to contact against the external meatus of the patient""s urethra. The biasing device operates to provide a pre-loading force on the catheter guide, thereby holding the catheter guide against the external meatus of the patient""s urethra such that the catheter securement device moves with the movement of the urethra. Additionally, the biasing device operates to push the catheter securement device against the supporting base, thereby minimizing unwanted motion of the catheter securement device within the suspension housing.
The catheter securement device is adapted to support the catheter in a manner such that the catheter moves in response to movement of the urethra, with the catheter remaining in generally the same position relative to the surrounding urethra when the patient coughs. In a preferred aspect, the catheter securement device comprises a torroidal balloon, a generally ring-shaped balloon support mount surrounding the torroidal balloon and a pneumatic or hydraulic pressure tube for inflating or deflating the torroidal balloon. The catheter passes longitudinally through the catheter holder and is received through the orifice defined by the torroidal balloon. Inflation of the torroidal balloon will cause it to expand radially inwardly such that it""s central orifice contracts, thereby gently pushing against the sides of the catheter.
In other preferred aspects of the invention, the catheter securement device comprises a mechanical clamp which is mounted to move longitudinally within the suspension housing.
Optionally, the present urethral catheter holder may also comprise a pair of leg straps, which can be wrapped around the patient""s thighs, (or a stretchable undergarment with leg straps attachable thereto), such that the supporting base of the catheter holder can be held at a generally fixed position against the labia of the patient. An advantage of such leg straps is that pressure measurements can then be taken easily with the patient in different positions, including supine and sitting. An additional advantage of the present system is that it allows hands-free operation for the clinician.